This patch addresses a few long-standing bugs and usability issues.

Retries have been corrected (previously if rdbfs had to retry, it
would always fail).

Setting the baudrate for the underlying serial console has also been
made optional.  Forcing the baudrate to 9600 causes issues on systems
that default to a different value.

Status was changed such that rdbfs processes now show up in the Broken
state with a meaningful user and name.  A note file was also added to
send a serial break on a kill note.

Reference: /n/sources/patch/maybe/rdbfs-retry-speed-broken
Date: Thu Jul  4 22:48:04 CES 2013
Signed-off-by: sstallion@gmail.com

--- /sys/man/4/rdbfs	Mon Aug 12 08:07:16 2013
+++ /sys/man/4/rdbfs	Mon Aug 12 08:07:03 2013
@@ -7,6 +7,10 @@
 .B -d
 ]
 [
+.B -b
+.I baudrate
+]
+[
 .B -p 
 .I pid
 ]
@@ -31,7 +35,10 @@
 a kernel over the serial line 
 .I device
 (default 
-.BR /dev/eia0 ).
+.BR /dev/eia0 ),
+optionally setting the baudrate if the
+.B -b
+option is specified.
 If the
 .B -s
 option is given,
--- /sys/src/cmd/rdbfs.c	Thu Jul  4 11:19:35 2013
+++ /sys/src/cmd/rdbfs.c	Thu Dec  5 21:51:35 2013
@@ -124,6 +124,7 @@
 	Xfpregs,
 	Xkregs,
 	Xmem,
+	Xnote,
 	Xproc,
 	Xregs,
 	Xtext,
@@ -134,6 +135,8 @@
 int	textfd;
 int	rfd;
 Biobuf	rfb;
+int	cfd;
+char*	baudrate;
 char*	portname = "/dev/eia0";
 char*	textfile = "/386/9pc";
 char*	procname = "1";
@@ -143,10 +146,21 @@
 void
 usage(void)
 {
-	fprint(2, "usage: rdbfs [-p procnum] [-s srvname] [-t textfile] [serialport]\n");
+	fprint(2, "usage: rdbfs [-b baudrate] [-p procnum] [-s srvname] [-t textfile] [serialport]\n");
 	exits("usage");
 }
 
+char *
+basename(char *s)
+{
+	char *p;
+
+	p = strrchr(s, '/');
+	if(p == nil)
+		return p;
+	return p+1;
+}
+
 void
 noalarm(void*, char *msg)
 {
@@ -224,9 +238,11 @@
 					goto Break2;
 				}else{
 					DBG(2, "unknown message\n");
+					break;
 				}
 			}
 		}
+		respond(r, "timed out");
 	Break2:;
 	}
 }
@@ -234,7 +250,6 @@
 void
 attachremote(char* name)
 {
-	int fd;
 	char buf[128];
 
 	print("attach %s\n", name);
@@ -243,11 +258,13 @@
 		sysfatal("can't open remote %s", name);
 
 	sprint(buf, "%sctl", name);
-	fd = open(buf, OWRITE);
-	if(fd < 0)
-		sysfatal("can't set baud rate on %s", buf);
-	write(fd, "B9600", 6);
-	close(fd);
+	cfd = open(buf, OWRITE);
+	if(cfd < 0)
+		sysfatal("can't open ctl %s", buf);
+
+	if(baudrate)
+		fprint(cfd, "b%s", baudrate);
+
 	Binit(&rfb, rfd, OREAD);
 }
 
@@ -301,7 +318,7 @@
 		respond(r, nil);
 		break;
 	case Xstatus:
-		n = sprint(buf, "%-28s%-28s%-28s", "remote", "system", "New");
+		n = sprint(buf, "%-28s%-28s%-28s", basename(portname), getuser(), "Broken");
 		for(i = 0; i < 9; i++)
 			n += sprint(buf+n, "%-12d", 0);
 		readstr(r, buf);
@@ -317,13 +334,15 @@
 {
 	char buf[ERRMAX];
 
+	r->ofcall.count = r->ifcall.count;
 	switch((uintptr)r->fid->file->aux) {
 	case Xctl:
+	case Xnote:
 		if(strncmp(r->ifcall.data, "kill", 4) == 0 ||
 		   strncmp(r->ifcall.data, "exit", 4) == 0) {
+			fprint(cfd, "k");
 			respond(r, nil);
-			postnote(PNGROUP, getpid(), "umount");
-			exits(nil);
+			threadexitsall(nil);
 		}else if(strncmp(r->ifcall.data, "refresh", 7) == 0){
 			flushcache();
 			respond(r, nil);
@@ -362,6 +381,7 @@
 	"fpregs",	Xfpregs,	0666,
 	"kregs",	Xkregs,		0666,
 	"mem",		Xmem,		0666,
+	"note",		Xnote,		0222,
 	"proc",		Xproc,		0444,
 	"regs",		Xregs,		0666,
 	"text",		Xtext,		0444,
@@ -392,6 +412,9 @@
 	case 'D':
 		chatty9p++;
 		break;
+	case 'b':
+		baudrate = EARGF(usage());
+		break;
 	case 'd':
 		dbg = 1;
 		break;
@@ -434,4 +457,3 @@
 	threadpostmountsrv(&fs, srvname, "/proc", MBEFORE);
 	exits(0);
 }
-